Preheating After Modular Inflation

TL;DR

This paper investigates non-perturbative preheating mechanisms in modular inflation models, revealing violent decay channels and analyzing energy transfer to the standard model sector with stringy effects considered.

Contribution

It identifies and analyzes strong non-perturbative preheating channels in modular inflation, including tachyonic instability and parametric resonance, and explores energy transfer scenarios with stringy effects.

Findings

Preheating can be dominated by tachyonic instability and broad-band parametric resonance.

Decay rates and reheat temperatures vary significantly depending on the scenario.

Stringy effects are crucial when the inflaton cycle shrinks to the string scale.

Abstract

We study (p)reheating in modular (closed string) inflationary scenarios, with a special emphasis on Kahler moduli/Roulette models. It is usually assumed that reheating in such models occurs through perturbative decays. However, we find that there are very strong non-perturbative preheating decay channels related to the particular shape of the inflaton potential (which is highly nonlinear and has a very steep minimum). Preheating after modular inflation, proceeding through a combination of tachyonic instability and broad-band parametric resonance, is perhaps the most violent example of preheating after inflation known in the literature. Further, we consider the subsequent transfer of energy to the standard model sector in scenarios where the standard model particles are confined to a D7-brane wrapping the inflationary blow-up cycle of the compactification manifold or, more interestingly, a non-inflationary blow up cycle. We explicitly identify the decay channels of the inflaton in these two scenarios. We also consider the case where the inflationary cycle shrinks to the string scale at the end of inflation; here a field theoretical treatment of reheating is insufficient and one must turn instead to a stringy description. We estimate the decay rate of the inflaton and the reheat temperature for various scenarios.